It's more a mistake to use a credit card at a retail store than PSN these days. I've had my CC info on PSN for years, yes the PSN hack happened, no issues beyond that. Long as it's not a debit card it's not a huge deal either, had unauthorized CC access a year ago, apparently due to a grocery store leak, had a new card in 24 hours and paid nothing. If you deleted your info I really wouldn't worry about it.
Seconded. They didn't even get anything useful in the 'hack', it was completely overblown. Everyone lost their shit because it took awhile to get back online, but that's because Sony and hired guns had to determine how the breach occurred, what exactly happened/was taken, and then had to implement better security from the ground up. I trust my CC there more than I do on sites that haven't been hacked (yet) because I know Sony has hired industry pros to make sure that never happens again.
Obviously, if you've got malware and spyware on your pc, or re-use the same simple pw everywhere, you are at risk for having your account (anywhere, not just PSN) hijacked, but that's a totally different thing.
As TapTap said, people feel 'safe' using their cc's at gas stations, diners, grocery stores, and chain stores and they're just as 'dangerous' -- either a shady clerk snatching your details, or, in the case of a place like Target, the big breach they had.
CC companies are extremely good at identifying and shutting down fraud quickly nowadays, and are easy to deal with in regards to getting fraudulent purchases removed. I'd say the only real issue would be account hijacking if you log in to the webstore with a malware'd computer... but assuming you take half-decent security precautions it's extremely low risk. And in this specific situation, where the details were only on for the time it took to purchase, it's 0 risk since even a hijack wouldn't be able to buy anything.